Partner is potentially suicidal
My boyfriend/partner is going through a very rough time and has had suicidal thoughts. When he gets like that, he feels that there is nothing good in his life and nothing will ever get better. He doesn't "hear" me when I tell him I love him and will stand by him and I think he's a wonderful person. He thinks he's a rotten person when in these moods. Yesterday he told me, in all seriousness, that I could put 99% of my marbles in this basket (our relationship continuing and growing into a forever "marriage"), but that I should save 1 marble out just in case he couldn't handle all this and had to "take himself out". He's leaving suicide in the mix of his options at this point! Even when he's in a good mood. This terrifies me! I don't know what I can do to help, if anything. I've told him he can call me night or day and I'll come be with him(we live about an hour from each other). I told him I will do whatever it takes to help him get through this. I guess I'm just looking for advice from someone who has dealt with a suicidal person and how I should respond to him and what I should do or say or not, when he's in the actual suicidal mood. It's only happened twice since we've been together (a year), but he is reaching some crises points in his life right now, and I'm afraid the frequency may increase.
Help please, even if it's just to share experiences.